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Headphones could eliminate MRI sounds

BioPhotonicsMay 2008
MRI scanners can make beeping, whirring and grinding sounds as loud as a jet engine. These sounds not only disturb patients but also cause some to squirm, thus ruining the images and wasting time and money.

Foam or other noise-deadening materials cannot reduce the sounds sufficiently. And although just about every consumer electronics or mass-retail store carries noise-canceling headphones, the electronics used in them would interfere with the magnetic field, distorting or ruining the images.

But engineering students at the University of Florida in Gainesville have developed noise-canceling headphones that the patient can wear in an MRI chamber. The devices were developed as part of a student challenge funded by Invivo Corp. of Orlando, Fla., a maker of MRI parts and accessories.

The students used headphones connected to hollow tubes reminiscent of those that flight attendants sold to airplane passengers in days of yore. They assembled the air headphones in a unique way, using two hollow tubes to pipe the sound outside the MRI chamber. The sound travels from the tubes to tiny microphones connected to an amplifier and a computer that processes the signal. The sounds trigger algorithms that instruct the computer to produce a sound signal opposite to the one received. The opposing sound travels through a third tube that forks and goes to headphones in the patient's ears. The sound waves cancel out, greatly reducing the noise the patient hears.

Trials of the system using a loud beeping sound similar to some MRI noises showed that it could reduce the noise by as much as 15 decibels. By comparison, ambient noise is about 60 decibels, with jet engines and other extremely loud noises reaching 120 decibels. Although the students did not come close to those numbers, they said further tweaks of the system and algorithm likely will improve the result.